A conventional lens in a camera works by accumulating visible light rays associated with an object, which are projected over a portion of a film or a digital camera optical sensor to form an image of the object. An optical zoom function of the camera may be used to change the magnification of the image before it is captured. A digital zoom may be used to change the magnification of an image after it has been captured.
An optical zoom arrangement may include a zoom lens whose focal length, and consequently the viewing distance and field of view of the camera, can be adjusted using the camera's optics, thereby changing the magnification of a projected image. A digital zoom arrangement may crop a captured image down to centered area with the same aspect ratio as the original image (and usually also interpolating the result back up to the pixel dimensions of the original).
The zoom in/zoom out functions of a camera may be activated by a user activating designated control buttons on the camera and/or touching icons on a touch screen of the camera, by which the image is displayed. Naturally, the use of such control buttons/icons occupies valuable, limited camera space and/or display screen space. Additionally, onscreen control icons may obstruct a portion of the displayed image.
Alternative activation zoom in/zoom out functions may involve a user making designated gestures, such as a clockwise or anticlockwise circle gesture, or a closing or opening pinch gesture, across a touch screen displaying an image. Such gestures may, however, obstruct part of the image being displayed while the user is zooming in/out, and gesturing may not be intuitively simple to some users or easy to perform while holding a camera steadily.